MIC was determined by modified broth microdilution method following the CLSI procedure. Vancomycin test concentration was in the range of 256 to 0.125 μg/mL. S. aureus ATCC 25923 was used as the control strain. MBC was determined following the CLSI procedure by plating 100 μL from the MIC, MIC × 2, MIC × 4 and MIC × 8 wells on LB agar and incubating the plates at 37°C overnight. The strains used here span the MIC range of P128.